Field of the Invention
The present invention relates to a communication apparatus that transmits an image file to an address on a network, a method of controlling the same, and a storage medium.
Description of the Related Art
S/MIME (Secure/Multipurpose Internet Mail Extensions) defined by RFC 2311 exists as a technology for improving electronic mail (e-mail) security. By using such a technology, encryption of e-mail data can be realized.
Internet facsimile apparatuses that attach image data read by a scanner to an e-mail and perform communication are also widely used, and a technology using S/MIME such as disclosed in Japanese Patent Laid-Open No. 2002-190891 also exists.
FIG. 18 is a diagram illustrating operations performed when one e-mail is broadcast to two addresses, namely, an address A and an address B.
A certificate 900 of a sender is encrypted using a secret key 901 of the sender to create a digest, and an electronic signature 902 is created together with public key information and the like. E-mail data 903 is encrypted using a common key 904 so that encrypted e-mail data 905 is generated.
Also, the common key 904 is encrypted using a public key 909 of a recipient A so that recipient A information 906 is created, and the common key 904 is encrypted using a public key 907 of a recipient B so that recipient B information 908 is created. The electronic signature 902, the encrypted e-mail data 905, the recipient A information 906, and the recipient B information 908 that were created in such a manner are converted into PKCS#7 format and sent.
S/MIME is not necessarily fully promulgated since management and operation of the keys are complicated. Accordingly, when one e-mail is broadcast to a plurality of addresses, not all the addresses necessarily support S/MIME. Also, depending on the importance of an e-mail or the network environment, there are cases where non-encrypted plain text data is transmitted to an address that does not support S/MIME without problem.
When, as described above, the plurality of addresses to which an e-mail is broadcast include an address that does not support S/MIME, a key encrypted using a public key of a recipient cannot be attached to that address. Therefore, even when the e-mail is received, the recipient can neither decode encrypted data in the e-mail nor check the content thereof. This is a significant problem particularly in a simple mode of an internet facsimile (IFAX) that does not enable a sender to be informed of the occurrence of an error.
Even in the case where an e-mail is transmitted while designating some of a plurality of destination addresses as Bcc (blind carbon copy), information on the recipient needs to be added to the transmission data, thus causing a problem in that information on recipients having a Bcc address is also disclosed.